1. Field of the Invention
The invention relates to ophthalmic and other types of surgical and non-surgical use blades. More particularly, the invention relates ophthalmic, micro-surgical and non-surgical blades manufactured from silicon and other crystalline materials.
2. Description of the Related Art
Existing surgical blades are manufactured via several different methodologies, each method having its own peculiar advantages and disadvantages. The most common method of manufacture is to mechanically grind stainless steel. The blade is subsequently honed (through a variety of different methods such as ultrasonic slurrying, mechanical abrasion and lapping) or is electrochemically polished to achieve a sharp edge. The advantage of these methods is that they are proven, economical processes to make disposable blades in high volume. The greatest disadvantage of these processes is that the edge quality is variable, in that achieving superior sharpness consistency is still a challenge. This is primarily due to the inherent limitations of the process itself. Blade edge radii can range from 30 nm to 1000 nm.
A relatively new method of blade manufacture employs coining of the stainless steel in lieu of grinding. The blade is subsequently electrochemically polished to achieve a sharp edge. This process has been found to be more economical than the grinding method. It has also been found to produce blades with better sharpness consistency. The disadvantage of this method is that the sharpness consistency is still less than that achieved by the diamond blade manufacturing process. The use of metal blades in soft tissue surgery is prevalent today due to their disposable cost and their improved quality.
Diamond blades are the gold standard in sharpness in many surgical markets, especially in the ophthalmic surgery market. Diamond blades are known to be able to cleanly cut soft tissue with minimal tissue resistance. The use of diamond blades is also desired due to their consistent sharpness, cut after cut. Most high-volume surgeons will use diamond blades since the ultimate sharpness and sharpness variability of metal blades is inferior to that of diamond. The manufacturing process used to make diamond blades employs a lapping process to achieve an exquisitely sharp and consistent edge radius. The resultant blade edge radii range from 5 nm to 30 nm. The disadvantage of this process is that it is slow and as a direct result, the cost to manufacture such diamond blades ranges from $500 to $5000. Therefore, these blades are sold for reuse applications. This process is currently used on other, less hard materials, such as rubies and sapphires, to achieve the same sharpness at a lesser cost. However, while less expensive than diamonds, ruby and/or sapphire surgical quality blades still suffer from the disadvantage that the cost of manufacture is relatively high, ranging from $50 to $500, and their edges only last through about two hundred cases. Therefore, these blades are sold for reuse and limited reuse applications.
There have been a few proposals for the manufacture of surgical blades using silicon. However, in one form or another, these processes are limited in their ability to manufacture blades in various configurations and at a disposable cost. Many of the prior proposals are based on anisotropic etching of silicon. The anisotropic etching process is one where the etching is highly directional, with different etch rates in different directions. This process can produce a sharp cutting edge. However, due to the nature of the process, it is limited by the blade shapes and included bevel angles that can be attained. Wet bulk anisotropic etching processes, such as those employing potassium hydroxide (KOH), ethylene-diamine/pyrcatechol (EDP) and trimethyl-2-hydroxethylammonium hydroxide (TMAH) baths, etch along a particular crystalline plane to achieve a sharp edge. This plane, typically the (111) plane in silicon <100>, is angled 54.7° from the surface plane in the silicon wafers. This creates a blade with an included bevel angle of 54.7°, which has been found to be clinically unacceptable in most surgical applications as too obtuse. This application is even worse when this technique is applied to making double bevel blades, for the included bevel angle is 109.4°. The process is further limited to the blade profiles that it can produce. The etch planes are arranged 90° to each other in the wafer. Therefore, only blades with rectangular profiles can be produced.
Thus, a need exists to manufacture blades that address the shortcomings of the methods discussed above. The system and method of the present invention can make blades with the sharpness of diamond blades at the disposable cost of the stainless steel methods. In addition, the system and method of the present invention can produce blades in high volume and with tight process control. Further, the system and method of the present invention can produce surgical and various other types of blades with both linear and non-linear blade bevels.